Currently, magnetic resonance imaging (MRI) is used one to three months after treatment to assess anatomic tumor response, based upon changes in tumor size and contrast-agent enhancement. Alternatively, diffusion-weighted imaging (DWI) can be used as a functional imaging technique to depict thermally induced motion of water molecules. The extent of water mobility within biologic tissues can be quantified by a parameter called the apparent diffusion coefficient (ADC). Recently, ADC values have been shown to change within days to weeks after therapy, which is earlier than changes seen by conventional HCC anatomic size assessment. However, no studies to date have reported the intraprocedural characteristics of ADC and whether these values can predict future tumor response at the time of chemoembolization.
A research article on the topic was published on July 7, 2010, in the World Journal of Gastroenterology. The research team led by Prof. Reed A Omary, from the department of radiology, Northwestern University (Chicago, IL, USA) used functional magnetic resonance imaging (fMRI) to measure alterations in tumor activity at the time of treatment, and compared them to tumor structural changes on traditional MRI scans at standard one- and three-months follow-up periods. The study's findings suggest that patients whose intraprocedural ADC values increase or decrease by > 15% are more likely to have a positive anatomic tumor response one month later.
This result is promising because early knowledge of HCC response after initial therapy is critical to revise prognosis and guide future therapy. Use of DWI and ADC mapping used with conventional anatomic imaging evaluation could additionally improve tumor response interpretation and subsequent treatment planning.
At present, MR/interventional radiology suites permit the acquisition of immediate quantitative functional imaging changes, in both tumor perfusion and now diffusion. Which of these two functional parameters is more effective as an intraprocedural biomarker to customize HCC therapy awaits verification by future studies, according to the investigators.
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